Method of and apparatus for dyring a continuous web



Aug. 20, 1935.

M. L. WOODRU FF METHOD OF AND APPARATUS FOR DRYING A CONTINUOUS WFLB DOUBLE (0 475,?

DRY/N6 DUCT cum/05mm; Rous STORAGE Filed Feb. 17, 1932 4 Sheets-Sheet l 'f' M M ATTORNEYS Aug. 20, 1935. M. L. WOODRUFF METHOD OF AND APPARATUS FOR DRYING A CONTINUOUS WEB Filed Feb. 17, 1952 4 Sheets-Sheet 2 W A L J M N. lw mm m N WM o |.V m EF- AM -1 m A W \N W 0 Q M 5. w 1w mxwww w! L J 1 v :mgafiw \QQ mi? Aug. 20, 1935. M. L. WOODRUFF METHOD OF AND APPARATUS FOR DRYING A CONTINUOUS WEB Fi1ed Feb. 1'7, 1932 4 Sheets-Sheet 5 NVENTOR 1; M Wm ATTORNEYS Aug. 20, 1935. M. 1.. WOODRUFF 2,012,115

METHOD OF AND APPARATUS FOR DRYING A CONTINUOUS WEB Filed Feb. 17, 1952 4 Sheets-Sheet 4 STEAM web drying phase UNITED STATES PATENT OFFICE METHOD OF AND APPARATUS FOR DRYING CONTINUOUS WEB Morgan L. Woodruff, Rumford, Maine, assignor to Oxford Paper Company,

corporation of Maine Application February 17, 1932, Serial No. 593,440

12 Claims.

This invention relates inter alia to the manufacture of coated paper, and on phases of the invention resides e of the salient in a method of and apparatus for drying a continuous web. The

larly applicable to the drying of of the invention is particua web of paper that has been coated on both surfaces, but other webs may be dried by the same the same apparatus.

method and with In the manufacture of coated paper, it is customary to coat one or both surfa ces of the paper with a wet solution or mixture containing, among other ingredients, water, clay, and pigment. Such casein, finely ground coating mixtures are well known in the paper manufacturing art and are usually referred to as the color.

of coated paper has long presente mercial problem, applied and smoothed out, the

The drying d a serious combecause (a) after the coating is wet paper cannot be allowed to contact with rolls or other supporting devices, and (b) the nature of the coating used is such that the application of high drying temperatures to it burns ruins the product.

For many years the used in actual practice for paper. ing the coating machine is passe over a-drying air that float the casein and festoon system has been the drying of coated In festoon drying the web of paper leavd for a distance table from which issue jets of heated the web and partially dry the coating. The drying eificiency of the drying table is so low that the web cannot be floated for the distance which would be required for complete drying. However, the drying table dries the coating sufficiently to permit the paper to be handled gingerly, series of slowly moving carried through a drying room.

and then it is draped in festoons over a bars on which it is slowly Festoon drying is obviously slow and cumbersome, and it requires a great deal drying operation. The festoone of space for the d paper cannot be moved rapidly and air cannot be rapidly circulated through the drying room, swing the loops of paper tact with one another. Attempts to speed up the drying and reduce the space redrying equipment by passing the quired for the web longitudinally through a due a blast of air is passed. Although because it would and bring them in conhave been made t through which numerous duct type driers have been designed, none has proved entirely satisfactory tice; and hence the that is actually used today in production of coated paper.

The dried coated paper is wavy,

in actual commercial pracold festoonsystem is the one the commercial and it has a dull New York, N. Y., a

be fed directly to calendering rolls because they 5 have to operate at high sped (in order to efiectively calender) and festoon driers can only handle the paper at relatively low speed.

For proper calendering it is very important that the moisture content of the paper be just right. If the paper is too wet, it discolors; and if it is too dry the finish produced is poor. No satisfactory means has been devised for determining the correct moisture content. An experienced operator judges it by running his hand over the web as it goes to the calendering roll. With the drying systems now in commercial use the moisture content of the dried paper is usually not correct for calendering, and in many instances the paper has to be steamed as it is passed from the reel to the calendering rolls.

A general object of the present invention is to provide a method of (and/or apparatus for) coating, drying and calendering paper by continuous operations, without intermediate reeling of the paper.

Other objects are to provide improved control in the drying of webs or the like; and specifically to provide for proper control of the moisture content of paper being calendered.

More specific objects of the invention are (a) to provide a commercially practicable method of (and/or apparatus for) drying continuous webs at considerably higher speeds than is possible with the festoon system, (b) to provide a commercially practicable web drying apparatus which economizes in space as compared to present commercial practice; and (c) to provide a method of (and/or apparatus for) drying a continuous web at high speed and low cost as compared to present commercial practice.

Figure 1 of the drawings shows diagrammatically a plan lay-out of the apparatus.

Figure 2 shows more or less diagrammatically a side elevation taken approximately on line 2-2 of Figure 1.

Figure 3 is a fragmentary side elevation (partially in section) showing the end of the drying duct at which the web enters and the drying air leaves the duct. The view is taken looking from the side opposite to that shown in Figure 2.

Figure 4 is a fragmentary side elevation (partially in section) corresponding to Figure 3, but showing the opposite end of the drying duct, 1. e.,

the end at which the web leaves and the drying air enters the duct.

Figure 5 is a vertical section through the dry-- ing duct, taken on line 55 of Figure 3.

Figure 6 is a vertical section through the drying duct, taken on line 66 of Figure 3.

Figure 7 is a detail plan view (partially in section) showing the air receiving end of the drying duct and the passages for distributing the drying air as it enters the drying duct.

Figure 8 shows diagrammatically control apparatus for automatically regulating the temperature and humidity of the drying air.

General arrangement of the apparatus Reference will first be had to Figures 1 and 2. A continuously moving web of paper I is coated on both sides by a coater 2, which may be of any known type suitable for high speed operation. The web leaves the coater and passes directly to a drying duct 4, where it is dried under controlled conditions to leave it with the correct moisture content desired for subsequent operations, e. g., calendering. From the drying duct the paper passes over tension rolls 3, and then to calendering rolls 5, after which it is wound upon storage rolls 6. Air heated by a steam heater I (of any suitable and known construction) is driven by a fan 8 through a conduit 9 that delivers the heated air to one end of the drying duct 4, preferably the end at which the paper leaves. The air moves longitudinally through the drying duct and leaves it at the opposite end through a conduit I0. Under control of an adjustable damper II, part of the air may be exhausted through conduit I2 to an exhaust stack, and the remainder of the air may be recirculated through con-duit I4 to the heater 1, where it is reheated and again passed through the drying duct 4.

Fresh air to compensate for the air exhausted through conduit I2 may be admitted to conduit I4 by any suitable'means. The means shown comprises a tunnel I5 open at both ends and attached to the outside of conduit I4. Adjacent the down stream end of tunnel I5 there is an opening in the side of conduit I4 at which there is pivoted a scoop-shaped inlet damper I6. Under the suction created by fan 8 and the air moving through conduit I4, fresh air is drawn through tunnel I5, and thence through the opening controlled by damper IB, to the interior of conduit I4. Damper I6 is adjustable to various positions to thereby vary the amount of fresh air admitted to conduit I4.

Fan 8 may be suitably driven by a variable speed drive to thereby regulate the speed of the air driven through conduit 9 and the drying duct 4, but further regulation of the air speed may be provided by means of a slide damper I1, which may be operated to close off conduit I4 to any desired extent.

The drying duct as a whole Referring to Figures 2, 3, and 4, it will be seen that the drying duct comprises an air-in section A, main drying sections B, B, B, and an air-out section C. It will, of course, be understood that the air is admitted to the drying duct at section A and leaves the drying duct at section C. The main drying sections B are all alike and any desired number of such sections B may be employed. The number of sections required depends upon various factors, such as the speed of the web, the nature of the web, the drying temperature and air velocity which can be employed, and the amount of moisture to be extracted from the web. The sections A, B, and C are, of course, connected together to form a continuous duct, and the entire duct may be supported by any suitable supporting structure D. The duct sections may each be fabricated in any suitable manner as by building them up from sheet iron suitably cut and welded; and the various duct sections may be assembled into one duct in any suitable manner as by bolting, riveting, or welding Main drying sections of drying duct The construction of the duct sections B is clearly shown in Figures 3, 4, 5, and 6. Each of these sections is symmetrical about a horizontal median plane, and the two halves are hinged together at 20 so that each section (and the whole duct) can be opened up after the manner of a book. The upper and lower halves are respectively provided with contacting longitudinally extending flanges 2| and 22, over which spring clamp members 23 may be forced to hold the duct closed.

In Figures 3 and 4, the web of paper I is moving to the right, and both above and beneath it layers of air are moving to the left. After passing through straight portion 25 of each duct section B, portions of the upper and lower layers of air are split ofi and flow through by-passes 26 and 21, respectively. These'by-passes 26 and 21 return the split off portions of the air to the main line of flow by impinging them substantially perpendicularly against the surface of the paper as indicated in Figure 3. Preferably the duct is so designed that its total cross sectional area at all points along its length is at least approximately a constant. Thus at section line 5-5 (Figure 3) the sum of the cross sectional areas of by-pass 26, the main passage adjacent the paper, and by-pass 21, is equal to the cross sectional area of the duct at section line 6-6.

It is apparent that the air stream impinging against the paper from by-pass 26 will tend to force the web downwardly, whereas the air stream impinging from the by-pass 21 will tend to force the web upwardly. Hence, the web I can be supported centrally of the duct by properly correlating the forces of the opposing air blasts. Dampers 30 and 3|, which extend transversely of the duct and are operable from the outside of the duct, may be manipulated to produce nozzle effects with locally increased velocity at the discharge ends of by-passes 26 and 21. Thus the forces of the opposing air blasts can be correlated as necessary to give the web the proper resultant support. Any number of windows 32 may be provided through which the web may be observed.

Air-in section of drying duct The conduit 9 is coupled to section A of the drying duct by a Y-shaped fitting to thereby deliver approximately half of the air above the web I and the remainder of the air below the web I. Section A is so constructed as to smoothly direct the incoming air and apply a layer of it to each surface of the moving web. The handling of the air by section A involves subdivision of the air streams and directing the subdivisions in such manner as to support the web, get the air gracefully moving longitudinally of the drying duct in the desired direction, and permit a large volume of air to be delivered to the drying duct without creating local pressure areas of a magnitude to cause unsatisfactory operation by whipping or deflecting the paper. The construction of the air-in end of the drying duct is best shown in Figures 4 and 7.

One leg of the Y-shaped fitting of conduit 9 (Figure 1) is coupled to a flange 40, and the other leg is coupled to a flange 4|. The air delivery system for the top half of the drying duct is symmetrical with respect to the air delivery system for the bottom half of the duct, and hence only the top half will be described in detail, but corresponding reference characters are applied to the bottom half. The two halves of the section are hinged together at 20*, so that by uncoupling the connection to flange 40, the section may be opened with the rest of the duct.

The incoming air first passes through a screen 42 and is then divided into four horizontal superimposed layers by partitions 44, 45, and 46. The first layer of air is fed through curved conduit 41 to an elongated nozzle 48 positioned transversely adjacent the paper web I so that as the web is about to leave the duct a fish-tail blast of air is delivered against the surface of the paper and inwardly of the. drying duct. The second layer of air is passed through a conduit 49 and delivered substantially perpendicularly against the surface of the web some distance before the web leaves the duct. The third layer of air is delivered through a conduit 50 and impinged against the surface of the web at a point closer to the exit of the paper from the duct. The last layer of air is delivered through a conduit and impinged against the surface of the web at a point still closer to the exit of the web from the duct.

Generally speaking, conduits 41,49, 50 and 5| are of rectangular cross section and have a width 9. little greater than the width of the web of paper I. Since the web of paper may be several feet wide, it is desirable that there be uniform lateral distribution of the air within .each of the conduits 41, 49, 50 and 5|. This is provided for by curved vertical deflectors in the entrance portion of each of'the conduits 41, 49, 59 and 5|. The curved vertical deflectors of conduits 41 and 49 are best shown in Figure '1, which is a plan view of the air-in end of the drying duct. In conduit 41 there are deflectors 41 41 and 41; and in conduit 49 there are deflectors 49 49 and 49. There are similar deflectors in conduits 50 and 5|, and they are indicated in dotted lines in Fig. 4.

The discharge ends of conduits 49, 50, and 5| are preferably provided with transverse control dampers 49 50 and 5N, respectively. Any desired number of windows 32 may be provided for observation of the web. Transversely extending slides 52 and 53 are movable toward and from the web to regulate the width of the exit slit through which the web leaves the duct.

It will be apparent that the entering air is so subdivided and controlled that a large volume of air can be smoothly and gracefully delivered to the duct without creating local pressure areas of a magnitude to whip the paper. .Also the admission of the air is in opposed streams which support the paper. The jets from upper and lower conduits 41 are such as to insure air flow through the drying duct in the desired direction and to minimize air leakage through the slit where the web leaves the duct.

Air-out section of the drying duct This section of the duct is best shown in Fig. 3.

"ingly, this portion It also is made in upper and lower halves which are symmetrical about a median horizontal plane and are hinged together at 20. Also any suitable number of observation windows 32 may be provided.

The oncoming stream of air is divided into three portions, one continuing on into center passage 54, and the other two passing through by-passes 55 and 56, respectively. By-passes 55 and 56, discharge the air in a backward direction against the surface of the mizing air leakage at the slit :where the web enters the duct. Also the discharge from bypasses 55 and 56 meets the current through center passage 54, thereby locally neutralizing the longitudinal flow in the duct and facilitating the discharge of the air laterally into discharge conduit (Fig. 1).

Discharge conduit I0 is coupled by a Y-shaped fitting (not shown) to flanges 51 and 51 The volume of air which is flowing laterally of the drying duct to discharge conduit 10 cumulatively increases as we progress transversely of the dry-, ing duct toward discharge conduit 10. Accordof duct section 0 is pyramidal in shape, with the base of the pyramid adjacent the plane of flanges 51 and 51 The web may pass to the drying duct directly from burnishing roll R. of the coater 2 (Fig. 1). This roll smooths the wet coating. It may be of a smooth brass roll so driven that its periphery moves in the direction of movement of web I, but at a very much higher linear speed than web I. The height of the slit through which the web enters the drying duct may be varied by adjustable slides 58 and 58 The flow through by-passes 55 and 56 may be regulated by adjustable dampers 59 and 59.

Temperature and humidity control of the drying air As previously explained in connection with Fig. 1, at least a portion of the drying air is recirculated and passed through the drying duct more than once. Two advantages of this are (a) the same air can pick up additional moisture on a second passage through the drying duct, and by reusing the air less fresh air has to be heated, and thus heat is saved; and (1)) since the recirculated air is moisture laden, it can be mixed with fresh air in such proportion as to control as desired the humidity of the air delivered to the drying duct. By proper humidity control of the drying air, together with proper coordination of the temperature and volume of the drying air and the speed at which the web I is moved, the moisture content of the dried (but not dehydrated) paper can be kept just right for future operations, e. g. calendering.

Means for automatically controlling the temperature and humidity of the air delivered to the drying duct are shown in Fig. 8. Within the duct 9 there is positioned a volatile liquid thermostat 60 connected to actuate a sylphon bellows BI and through it control a valve 62 that regulates the admission of steam to heater 1 (Fig. 1) Thermostat 60, and suitable valves to be actuated by it are well known and may be purchased on the open market.

Also'within the conduit 9 are bulbs 54 and 65 each containing a volatile fluid. One of these bulbs is kept wet by suitable means such as a wick, and thus the two bulbs act as wet and dry bulb thermostats. The wet and dry bulbs 64 and 65 are connected to mechanism 66, which web, thus miniresponds to the difference in pressures (corresponding to wet and dry bulb temperatures) to thereby actuate tongue 61 in response to changes damper II (which controls the recirculation) are automatically actuated to regulate the humidity of the air delivered to the drying duct through conduit 9. The control apparatus include slip ring 19 and make-and-break 1|, both carried by shaft 12, which is continuously rotated by any suitable means. Under the control of relays 13 and 14, connection is made as required from power line 15 to motor 16 to effect the movement of dampers II and I6.

Assume that the humidity of the air in conduit 9 is higher than the value which the apparatus is set to maintain. Tongue 61 will move upwardly, engaging contact 11 and completing a circuit from battery 18 through the winding of the relay 13, thereby causing the relay to pick up. When the conducting sector of make-and-break 1| engages brush 19, circuit will be completed from the negative side of power line 15, slip ring 10, shaft 12, brush 19, relay armature 89, contact 8|, armature of motor 16, and then to the positive side of power line 15. The field of the motor (D. C. shunt motor) is energized from the positive side of line 15, relay armature 82, contact 84, through the field of the motor to contact 85, relay armature 86, conductor 81, brush 19, conducting segments of make-and-break 1|, shaft 12, and slip ring 16 to the negative side of the power line 15. This causes the motor 16 to rotate and give an increment of movement to dampers II and I6 in such direction as to further open damper I6 and move damper I I to divert more of the outcoming air to the exhaust stack I2. Thus the amount of moisture laden air returned to the drying duct will be diminished and the amount of fresh air will be correspondingly increased, thereby reducing the humidity of the drying air delivered to the drying duct.

Make-and-break 1 I, the speed of motor 16, and the gearing to dampers II and I6 are so designed and correlated that a suitable increment of movement will be given to the dampers I I and I6 while the conducting segment of make-and-break 1| is in contact with brush 19. No further movement of dampers II and I6 can take place until the conducting segment of make-and-break 1| again contacts with brush 19, and thus a suitable time interval is provided to give the apparatus a chance to respond to the change in damper positions. If the humidity is still too high when the conducting segment of make-and-break 1I again contacts with brush 19, tongue 61 will still be'in engagement with contact 11 and hence a second similar increment of movement will be given to dampers I I and I6. Thus adjustment of the dampers continues step-by-step until the humidity has reached the value for which the apparatus is set to regulate. Then tongue 61 will move to neutral position and no further movement of the dampers II and I6 will take place until the humidity again varies from the desired value.

Assume that the humidity of the air passing through conduit 9 is less than the value for which the apparatus is set to regulate. Tongue 61 then moves downwardly, engaging contact 83. This completes a circuit from battery 18, through contact 83, to the winding of relay 14, causing this relay to pick up. When the conducting sector of make-and-break 1| engages brush 19, circuit is completed (in the same direction as before) to the armature of motor 16 as follows: negative side of line 15, slip ring 10, shaft 12, brush 19, conductor 81, relay armature 88, contact 89, armature of motor 16, and then to the positive side of power line 15. Circuit is also completed from power line 15 to the field of motor 16, but the polarity of the connection is reversed, so as to cause the motor 16 to rotate in the opposite direction. The circuit through the field of motor 16 is from the positive side of power line 15, relay armature 82, contact 98, field winding of motor 16, contact 9|, relay armature 86, conductor 81, brush 19, shaft 12, slip ring 18, to the negative side of power line 15. Thus, the motor 16 is energized to give a suitable increment of movement to each of dampers II and I6, damper I6 being moved toward closed position, and damper I I being moved to divert less of the moisture laden air to the exhaust stack I2. Accordingly the humidity of the air delivered to conduit 9 is increased. If the humidity is still too low when the conducting sector of make-and-break 1| again contacts with brush 19, a further similar increment of movement will be given to dampers I6 and II, to further increase the humidity. When the humidity reaches the correct value, tongue 61 will move to neutral position and dampers II and I6 will remain stationary.

It will be apparent that under the control of Wet and dry bulbs 64 and 65, the dampers I I and I6 are automatically manipulated to maintain the humidity at the given value which the apparatus is set to regulate. be sufiicient to actuate only one of dampers Ii and I6 automatically instead of actuating both of the dampers. Motor 16 should, of course, be of the proper speed to give a sufficiently small increment of movement to the dampers at each energization of the motor. If a sufficiently low speed motor is not available, it can, of course, be geared down as required.

Air temperature and velocity The rate of evaporation rises rapidly with increase of temperature of the drying air, but in the past it has not been possible to use high temperature drying air, because of burning of the casein in the coating. Experience has shown that with the drying systems previously used, the highest suitable temperature for the drying air is about 140 Fahrenheit. Also the rate of evaporation rises rapidly with increase of the air velocity (provided the air is actually in contact with the paper) but with the festoon system of drying, high air speed is impossible, as has been previously explained. With the duct type driers suggested in the prior art, whipping of the paper and inadequate support of the paper precluded the circulating of the drying air at high speed. Furthermore, high air speed in the previously suggested duct type driers would be largely ineffective, because in those driers such a small portion of the air makes adequate contact with the paper.

I have found that the casein or coating material is able to withstand high temperature air for a very brief time. Therefore, if the dry- In some instances it may ing can be completed in this brief time, high temperature drying air can be used. By the method and apparatus disclosed, I am able to so support the paper that a large volume of drying air can be employed, which with the repeated impinging of the drying air against the surface of the web, speeds up the drying to a point permitting the use of high temperature drying air. Thus, I am able by this method to take advantage of the increased rate of evaporation of high temperature air without burning v may be used for drying other webs than webs of coated paper, though the invention is particu-- larly adapted to drying paper coated on both sides. Drying mediums other than air may be employed, but air is usually the most readily available medium, and hence it has been specifically referred to. Of course, the method disclosed may be practiced by a variety of different forms of apparatus; and many changes may be made in applicants apparatus without departing from the invention. Accordingly, the disclosure is merely illustrative in compliance with the patent statutes and is not to be considered as limiting the scope of the invention.

Having thus described my invention what I claim is:

1. The method of drying a continuous web which comprises continuously moving the web longitudinally of itself, applying a main layerof fiuig an drying medium to each surface of the web moving the layers relative to the web and longitudinally thereof, repeatedly splitting off portions off each drying layer which are not in contact with the web and forming such split-off portions into separate streams, and repeatedly impinging such separate streams against the surface of the web and thereby returning them to the main drying layers.

2. The method of drying a continuous web which comprises continuously moving the web longitudinally of itself, applying a main layer of fluid drying medium to each surface of the web and moving the layers longitudinally of the web in the direction opposite to the web movement, repeatedly splitting ofi portions of each drying layer which are not in contact with the web and forming such split-off portions into separate streams, and repeatedly impinging such separate streams against the surface of the web and thereby returning them to the main layers.

3. The method of supporting a web in a duct which comprises forcing a blast of gas longitudinally through the duct, removing portions of the gas from the duct proper at at least one position along the duct, and returning the removed portions to the duct proper and impinging them against the web.

4. The method of keeping a web out of contact with a duct which comprises forcing a blast of gas longitudinally through the duct on opposite sides of the web; at at least one point along the duct, removin portions of the gas on opposite however, the air speed 5 sides of the web fr\om the duct proper by directing them gradually away from the direction of travel in the duct; and returning the removed portions to the duct proper and impinging them at a sharp angle against opposite sides of the web.

5. The method of keeping a web out of contact with aduct which comprises forcing a blast of gas longitudinally through the duct on opposite sides of the web; at a\plurality-of points along the duct, removing portions of the gas on opposite sides of the web from the duct proper by directing them gradually away from the direction of travel in the duct; and returning theremoved portions to the duct proper and impinging them at a sharp angle against opposite sides of the web.

'6. Drying apparatus comprising an elongated duct; means to force a fluid longitudinally through the duct from end to end thereof; and at least one pair of opposed by-passes extending longitudinally of the duct, said by-passes being effective to withdraw fluid from the duct, convey it longitudinally of the duct and return it thereto farther downstream in opposed streams.

7. Drying apparatus comprising an elongated duct; means to force a fluid longitudinally through the duct from end to end thereof; at least one pair of opposed by-passes extending longitudinally of. the duct, said by-passes being effective to withdraw-fluid from the duct, convey it longitudinally of the duct and return it thereto farther downstream in opposed streams; and means to control the flow through the by-passes.

8. In a drying duct; a fluid exit section at one end of the duct comprising by-passes extending longitudinally of the duct, said by-passes being effective to withdraw fluid from the duct before it reaches the end of the duct and return it longitudinally to the duct at its end; and means to discharge fluid laterally from the duct.

9. Drying apparatus comprising an elongated duct; means to force a fluid longitudinally through the duct from end to end thereof; at least one pair of opposed by-passes extending longitudinally of the duct, said by-passes being. effective to withdraw fluid from the duct, convey it longitudinally of the duct and return it thereto in opposed streams; and control dampers adjacent the discharge ends of said by-passes.

10. The method of drying a web of coated paper which comprises heating a. fluid drying medium to a temperature in excess of 200 degrees Fahrenheit, moving a main stream of the drying medium at such temperature in contact with and longitudinally of the web at a speed relative to the web of over 1800 feet per minute, repeatedly splitting off portions from the main stream and forming such split-off portions into separate streams, and then impinging such separate streams against the web and thereby returning them to the main stream.

11. The method of drying a web of paper having on its surface a wet coating containing organic material which comprises heating a fluid drying medium to a temperature in excess of 200 degrees Fahrenheit and under 501 degrees Fahrenheit, moving a stream of the medium at such temperature in contact with the web at a speed relative to the web of over 1800 feet per minute and under 5001 feet per minute, and removing the paper from the influence of the heated dryingv medium as soon as the desired dryness of the paper has been attained. i 

